Field of the Invention
The present invention relates to a microscope apparatus, and more particularly, to a microscope apparatus including a photodetector having an angular characteristic.
Description of the Related Art
In recent years, the demand for observing deep portions of living tissue, such as the hippocampus of the brain of a living mouse or the like, has been increasing. Since living tissue is a strongly scattering medium, it is preferable to use a near infrared ray that has low invasiveness and a highly scattering transmittance for an observation of living tissue. Therefore, attention has been focused on a multi-photon excitation laser scanning microscope (hereinafter abbreviated to MPE-LSM) using a near infrared ray.
Even when living tissue is excited with a near infrared ray, fluorescence generated by the living tissue cannot be prevented from being scattered within the living tissue. Accordingly, for an MPE-LSM, various schemes for efficiently guiding fluorescence that scatters in a wide range within a living tissue to a photodetector are proposed.
For example, a scheme for increasing an effective diameter of an optical element such as an objective, a relay optics system, a filter or the like, arranged on a light path from a living tissue to a photodetector, so as to reduce a vignetting of an off-axis light beam is known. Moreover, Japanese Laid-open Patent Publication No. 2013-156467 discloses a technique for suppressing a vignetting of an off-axis light beam caused by a housing that accommodates a detection element.